Habitat

Microgale gracilis prefers the eastern humid forests of Madagascar. Specimens have been recorded in valley bottoms with dense vegetation in moist, subtropical, montane areas from 1,200 m to 1,990 m elevation. Nearly all Microgale species live sympatrically in at some point in their geographic range (e.g., all species have been recorded in the Andringitra National Park), however, M. gracilis lives at a higher elevation than most Microgale. (Garbutt, 2007; Goodman and Benstead, 2003; Wilson and Reeder, 2005)

Physical Description

Like other members of its family, Microgale gracilis retains many primitive traits, including a low and seasonally variable body temperature, a cloaca (common opening for the urogenital, anal and reproductive tracts) and testes that are undescended in the male. Microgale gracilis is shrew-like in appearance and many of its morphological features suggest that it is semi-fossorial. This species is characterized by an elongate skull, long rostrum and rhinarium, dense, velvety pelage, reduced eyes and ears, short forelimbs with broadened forefeet, and enlarged claws with five digits. The tail is shorter than the head/body length. Individuals have dark-brown dorsal pelage with buff speckles, and dark grey ventral pelage with a "buff wash." The tail is bicoloured, dark brown dorsally and light brown ventrally. Juveniles appear less speckled than adults, particularly posteriorly. The dentition is much reduced in size with slender canines and incisors. The adult dental formula of M. gracilis is I3/3, C1/1, P3/3, M3/3. (Garbutt, 2007; Goodman and Benstead, 2003; Macdonald, 1987)

Microgale gracilis may be confused with Microgale gymnoryncha, but the two can be differentiated by the posterior region of the rhinarium, which is reticulated in M. gracilis. Also, the braincase length is generally less than 8.5 mm in M. gracilis and greater than 8.5 mm in M. gymoryncha. (Goodman and Benstead, 2003)

Basal metabolic rate of M. gracilis is unknown, but there is information on closely related species. The field metabolic rate (FMR) for nonreproducing Microgale dobsoni is 77.1 kJ/d (mean body mass 42.6 g), which is 3.8 times the resting metabolic rate (RMR) of the species. Also, the mean FMR for nonreproducing M. talazaci (mean body mass 42.8 g) is 66.5 kJ/d, which is 3.2 times RMR. (Stephenson, 1994)

Microgale gracilis becomes sexually mature after the formation of adult dentition, however, little else is know of the reproductive behavior of this species. All species of the family Tenrecidae that have been studied have relatively long gestation periods. Though Microgale are nearly the same size as a true shrew, their gestation period is almost twice as long (eight weeks versus three to four weeks in a shrew). Litter size of related Microgale species tend to be small, with a maximum of three. All Tenrecidae lack a fluid-filled cavity (antrum) that develops in the ovarian follicle. Before ovulation, spermatozoa contact and penetrate the developing follicles, fertilizing the egg before ovulation. The only other mammal in which this occurs is Blarina brevicauda (the short-tailed shrew). Microgale gracilis can have up to six mammae. (Goodman and Benstead, 2003; Macdonald, 1987; Stephenson, 2007)

Size at birth of and the timing of ontogenetic events of Microgale gracilis young is unknown. However, Microgale dobsoni offspring weigh 3.95 g at birth, on average and are fully furred by 18 to 22 days after birth. Most M. dobsoni young are weaned by 28 to 30 days, become sexually mature by about 2 years old, and weigh an average of 37.8 g upon reaching independence. (De Magalhaes and Costa, 2009)

No information is available regarding parental care in Microgale gracilis. As mammals, females likely invest much time and energy in their young until they are weaned. Evidence from closely related Microgale species (M. talazaci and M. dobsoni) suggests that offspring are weaned by 28 to 30 days, then followed the mother at night as she forages. Following behavior by young suggests that mothers may protect offspring prior to independence. There is no information on post-independence associations between mother and offspring. (Eisenberg and Maliniak, 1985; Walker, 1964)

Behavior

Little is known of the general behavior of Microgale gracilis. This species is not arboreal or scansorial like many Microgale species. Morphological traits suggest a semi-fossorial behavior (e.g., small eyes, small ears, short, dense pelage). Microgale gracilis is terrestrial, nocturnal and forages alone, suggesting that it is solitary. (Garbutt, 2007; Goodman and Benstead, 2003)

Predation

No information is available concerning the major predators of Microgale gracilis. However, this species is probably prey for small carnivores, birds of prey, snakes and other Microgale. Remains of the closely related species (M. melanorrhachis and M. talazaci have been found in the scat of fossas and in barn owl pellets, and both Microgale species occur sympatrically with M. gracilis. There is no information on anti-predator adaptions of Microgale gracilis or closely related species, however, its suggested fossorial and nocturnal lifestyle may help reduce risk of predation. (Goodman, et al., 1997; Stephenson, 2007)

Economic Importance for Humans: Negative

Conservation Status

Microgale gracilis is classified asa species of "least concern" on the IUCN's Red List of Threatened Species. Despite this, however, its numbers are decreasing and deforestation of Madagascan rainforests may lead to further decline of this species. Many primary forests in Madagascar are being logged to provide land for agriculture, and the ability of M. gracilis to survive in second growth forests is unknown. More research is needed to gain a better understanding of the potential conservation needs of this species. (Jenkins and Raherisehena, 2008a; Stephenson, 2007; Wilson and Reeder, 2005)

Contributors

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

insectivore

An animal that eats mainly insects or spiders.

island endemic

animals that live only on an island or set of islands.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

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The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.